In this research, particle size effect on heat transfer and hydrodynamics of a nonreactive gas-solid fluidizedbed reactor were studied experimentally and computationally. A multifluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady-state behavior of this reactor and momentum exchange coefficients were calculated by using the Syamlal-O'Brien drag functions. Simulation results were compared with the experimental data to validate the computational fluid dynamics (CFD) model. Pressure drops and temperature distribution predicted by the simulations at different particle sizes were in good agreement with experimental measurements at superficial gas velocity higher than the minimum fluidization velocity. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upward forming larger bubbles. The influence of solid particles size on the gas temperature was studied. The results indicated that, for smaller particle size, due to a higher heat-transfer coefficient between the gas and solid phases, solid-phase temperature increases and mean gas temperature decrease, rapidly. Furthermore, this comparison showed that the model can predict hydrodynamic and heat-transfer behavior of gas-solid fluidized-bed reactors reasonably well.
In this paper, a dielectric barrier discharge cylindrical reactor has been analyzed in order to increase the efficiency of nitrogen oxide (NO x ) removal from the simulated gas under the room temperature. The effects of electrode shape as well as electrode diameter and electrode length are investigated in the nonthermal plasma reactor. Two different electrode configurations (rod and screw thread electrodes) are examined. The experimental result shows that for the rod electrode, NO x removal efficiency is enhanced by increasing the electrode diameter. However, the screw thread electrode is more effective in decreasing NO x concentration. Finally, the results showed that the average input power requirement for NO x removal can be reduced almost 14% using a 1-mm screw thread electrode instead of a rod electrode.Index Terms-Dielectric barrier discharge (DBD) reactor, electrode configuration, NO x removal, nonthermal plasma (NTP), rod electrode, screw thread electrode.
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